Agricultural photoelectric conversion film synthesis method based on selective spectral regulation and application

Abstract

The application discloses a kind of based on selective spectral regulation agricultural photoelectric conversion film synthesis method and application, belong to the cross field of agricultural technology and new energy.It is quantum dot as core spectral selective absorption material in the synthesis method, by the standardization steps of substrate pretreatment, transparent electrode preparation, photoelectric conversion layer coating, quantum dot layer integration, back electrode evaporation and packaging, the functional film comprising "substrate-transparent electrode-photoelectric conversion layer-quantum dot spectral selective absorption layer-back electrode" is prepared.The quantum dot layer can efficiently absorb the ultraviolet light, green light and near-infrared light with low photosynthesis utilization rate of plant, and energy is transferred to photoelectric conversion layer to realize power generation;At the same time, the transmittance of blue light and red light necessary for plants is greater than or equal to 85%.The synthesis process of the application has strong compatibility and high repeatability, solves the contradiction between power generation and planting in traditional "agri-photovoltaic", realizes light energy hierarchical utilization and agri-photovoltaic synergy, and can be widely applied to greenhouse, greenhouse, plant factory and other agricultural facilities cover.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of agricultural technology and new energy, specifically relating to a method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation and their application as agricultural facility coverings. Background Technology

[0002] With the rapid development of the new energy industry and modern agriculture, the "agricultural-solar complementary" model has become an important direction for realizing the comprehensive utilization of land resources. However, existing technologies still have many problems that need to be solved. The following comparison of the advantages and disadvantages of two mainstream related technologies clarifies the technical advantages of this invention: Quantum dot light-converting films (non-photoelectric conversion type) possess a certain spectral conversion capability, converting ultraviolet light into visible light, thus partially reducing the damage of ultraviolet light to crops. Using polyethylene (PE) as the matrix, they offer good flexibility and are suitable for agricultural mulching applications. However, they can only achieve spectral conversion and cannot convert non-essential light into electrical energy, resulting in low light energy utilization. Furthermore, their light-converting function is limited, failing to simultaneously absorb green and near-infrared light, thus not resolving the conflict between agricultural and solar energy.

[0003] Semi-transparent silicon-based photovoltaic films can directly achieve photoelectric conversion and have strong power generation stability; the technology is mature and large-scale production is easy. However, they have uniform and non-selective spectral transmission, but low transmittance of blue and red light, which seriously affects crop photosynthesis; the photoelectric conversion efficiency is low and the shading rate is high; the material is brittle and has poor flexibility, making it unsuitable for the covering needs of curved greenhouses; the preparation process is energy-intensive and costly.

[0004] In summary, the core contradictions of existing technologies lie in either a lack of photoelectric conversion capabilities, resulting in low light energy utilization, or poor spectral selectivity, sacrificing crop growth for power generation; and the absence of an integrated process for customized quantum dot synthesis and thin-film integration, leading to insufficient spectral matching and practicality. This invention precisely addresses these technical pain points through customized quantum dot synthesis and optimized thin-film structure. Summary of the Invention

[0005] To address the core contradiction in existing "agricultural-photovoltaic complementary" technologies—the competition between power generation and plant growth for light—as well as the problems of poor spectral selectivity, low light energy utilization, and insufficient compatibility between quantum dots and thin films, this invention provides a method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation. This method achieves the function of "absorbing waste light to generate electricity and transmitting necessary light to promote growth," thereby improving light energy utilization and agricultural economic benefits.

[0006] The objective of this invention is achieved through the following technical solution: 1. Select a transparent flexible polymer film as the substrate, and remove surface impurities by cleaning and drying. The polymer film is a transparent flexible film made of polyethylene terephthalate, polyethylene naphthalate, or polycarbonate. It has good light transmittance (≥90%) and flexibility, and can be adapted to the needs of greenhouse arc covering. The thickness is controlled at 80-120μm to balance strength and light transmittance, with a light transmittance of ≥90%. 2. A transparent conductive layer with a thickness of 40-60 nm is prepared on the pretreated substrate surface by spin coating or sputtering. The transparent conductive layer material is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or indium tin oxide (ITO), with a thickness of 40-60 nm, which ensures conductivity while reducing light absorption and avoids affecting the light transmission required by the plant. The specific preparation method is as follows: (1) Spin-coating a 1.0-1.5wt% PEDOT:PSS aqueous solution at a speed of 2500-3500rpm for 20-40 seconds, and then annealing at 110-130℃ for 20-30 minutes to obtain a PEDOT:PSS transparent conductive layer. (2) ITO transparent conductive layer was prepared by magnetron sputtering. a. Preparation before sputtering: Fix the pretreated substrate onto the magnetron sputtering stage, seal the chamber, and evacuate to a background vacuum level ≤5×10⁻⁶. -4 Pa; In2O3 with a purity of 99.99% and SnO2 were mixed in a molar ratio of 90:10 as the ITO ceramic target material; b. Target pre-sputtering: Introduce argon gas with a purity of 99.999%, adjust the flow rate to 25-35 sccm, control the working gas pressure to 0.2-0.4 Pa, apply 120-180W RF power, and turn off the stage baffle to pre-sputter the target for 8-12 minutes. c. Keep the argon flow rate and working pressure constant, adjust the RF power to 180-220W, open the stage baffle, control the stage rotation speed to 10-20r / min, and deposit to the target film thickness of 40-60nm at a sputtering rate of 0.08-0.12nm / s. d. After deposition, the sample is heated to 170-190℃ at a heating rate of 4-6℃ / min, and annealed at a constant temperature for 25-35 minutes. The sample is then cooled in the furnace to obtain the ITO transparent conductive layer.

[0007] 3. A photoelectric conversion material is coated on the surface of the transparent conductive layer, and after annealing and curing, a photoelectric conversion layer is formed on the transparent conductive layer; The photoelectric conversion materials are poly(3-hexylthiophene) and (6,6)-phenyl-C 61 A mixture of methyl butyrate (P3HT:PCBM), perovskite material, with a coating thickness of 80-120 nm, comprising poly(3-hexylthiophene) and (6,6)-phenyl-C61 The mixture of methyl butyrate and P3HT was prepared by dissolving P3HT and PCBM in chlorobenzene at a mass ratio of 1:0.8-1:1 to form a mixed solution with a concentration of 15-25 mg / mL; the perovskite material used was Cs. 0.1 FA 0.9 PbI 2.8 Br 0.2 It was prepared into a liquid with a concentration of 40 wt%; 4. Core-shell structured quantum dots are synthesized by hot injection method, and then dispersed in organic solvent to prepare a quantum dot solution with a concentration of 3-8 mg / mL. The solution is then coated onto the surface of the photoelectric conversion layer by spin coating or blade coating, and dried to form a quantum dot spectrally selective absorption layer. The core-shell quantum dots are CdSe / ZnS, CdTe / ZnS, or PbS / CdS, with a particle size of 5-10 nm and a fluorescence yield ≥75%. The concentration of the quantum dot solution is 3-8 mg / mL, prepared using n-hexane, chlorobenzene, or toluene. The synthesis of the core-shell quantum dots is as follows: (1) Preparation of metal precursor solution, non-metal precursor solution, and shell precursor solution; (2) Heating an octadecene solvent containing oleic acid, oleylamine or trioctylphosphine ligand to 280-300°C, rapidly injecting it into the metal precursor solution and the non-metal precursor solution, reacting at 280-300°C for 10-30 minutes to form monodisperse quantum dot nuclei; (3) Perform segmented heating shell coating. Reduce the temperature of the reaction system to the basic coating temperature of 220-250℃, inject the shell precursor solution at a rate of 0.5-2 mL / min, and react at a constant temperature of 220-250℃ for 10-20 minutes to complete the initial uniform deposition of the shell on the surface of the quantum dot core. Then, heat the system in segments at a heating rate of 5-10℃ / min to the crystallization temperature of 240-260℃ and react at a constant temperature for 10-40 minutes to form a densely coated core-shell structure. After centrifugation, solid washing, and drying, the core-shell structured quantum dots are obtained. The core-shell quantum dot is configured to selectively absorb ultraviolet light with wavelengths <400nm, green light with wavelengths of 500-600nm, and near-infrared light with wavelengths >700nm, and guide the absorbed light energy to the photoelectric conversion layer through exciton energy transfer to achieve photoelectric conversion; the transmittance of ≥85% for blue light with wavelengths of 400-500nm and red light with wavelengths of 600-700nm, which are essential for plant photosynthesis.

[0008] The precursor solution is a cadmium salt solution or a lead salt solution; the non-metallic precursor is a selenium source solution, a tellurium source solution, or a sulfur source solution; and the shell precursor is a zinc-sulfur solution or a CdS solution. The selenium source is selenium powder or trioctylphosphine selenium; the sulfur source is sulfur powder or trioctylphosphine sulfur; and the tellurium source is tellurium powder or trioctylphosphine tellurium. The quantum dot spectrally selective absorption layer absorbs light in the first preset wavelength band and guides it to the photoelectric conversion layer, with a transmittance of ≥80% for light in the second preset wavelength band. The first preset wavelength band includes ultraviolet light with a wavelength <400nm, green light with a wavelength of 500-600nm, and / or near-infrared light with a wavelength >700nm. The second preset wavelength band includes blue light with a wavelength of 400-500nm and red light with a wavelength of 600-700nm. 5. A metal back electrode layer is prepared on the surface of the quantum dot spectrally selective absorption layer by vacuum evaporation; Back electrode: An ultra-thin silver semi-transparent back electrode layer with a thickness of 10-20 nm is prepared by vacuum evaporation to ensure effective charge collection; 6. Packaging The multilayer composite material prepared above is encapsulated with UV-curable resin or polyimide film to obtain an agricultural photoelectric conversion film, which improves the film's weather resistance and meets the long-term outdoor use requirements of agricultural facilities.

[0009] Advantages and technical effects of the present invention: (1) Precise spectral regulation: By using the thermal injection method to customize the synthesis of quantum dots, the energy requirements of the plant's non-essential light absorption and photoelectric conversion layer can be precisely matched. After spectrophotometer testing, the transmission peaks are formed in the blue and red light bands, and the transmittance of blue and red light is ≥85%, which is highly matched with the spectral response of plant photosynthesis, ensuring the normal growth of crops. (2) High-efficiency photoelectric conversion: The photoelectric conversion layer is precisely matched with the energy transfer band of the customized quantum dots, and the photoelectric conversion efficiency reaches more than 5%; (3) Integrated process: The process of "quantum dot synthesis-thin film integration" is integrated, and the particle size and fluorescence yield of quantum dots are controllable and highly reproducible; (4) Strong agricultural adaptability: The film is flexible and can be fitted to cover agricultural facilities of different shapes. After encapsulation, it has excellent weather resistance and can work stably for ≥1 year when used outdoors. (5) Significant economic benefits: Photovoltaic power generation and crop planting can be realized simultaneously without occupying additional land, and the revenue from power generation can be used to support agricultural production. Attached Figure Description

[0010] Figure 1 The diagram shows the layered structure of the thin film of the present invention, which, from bottom to top, consists of: a substrate, a transparent conductive layer, a photoelectric conversion layer, a quantum dot spectrally selective absorption layer, a metal back electrode layer, and an encapsulation layer. Figure 2 The graphs show the spectral response curves of the thin film of the present invention. Curve 1: Quantum dot absorption spectrum, covering the ultraviolet, green, and near-infrared bands; Curve 2: Thin film transmission spectrum, with transmission peaks in the blue and red bands; Curve 3: Spectral response curve of plant photosynthesis. Figure 3The figures show a comparison of the performance of the thin films prepared in different embodiments, with the upper figure showing transmittance data for different wavelengths and the lower figure showing the photoelectric conversion efficiency test results. Detailed Implementation

[0011] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, the scope of protection of the present invention is not limited to the contents described. Unless otherwise specified, the reagents and methods used in the embodiments are all commercially available reagents and conventional methods. Example 1: Preparation of CdSe / ZnS quantum dot + P3HT:PCBM photoelectric conversion thin film 1. Quantum dot synthesis materials: cadmium chloride, selenium powder, zinc chloride, sulfur powder, oleic acid, oleylamine, trioctylphosphine, octadecene (all analytical grade); substrate: PET film (100μm thickness); transparent electrode material: PEDOT:PSS aqueous solution (1.3wt%); photoelectric conversion materials: P3HT, PCBM; quantum dots: CdSe / ZnS core-shell structure quantum dots; organic solvents: n-hexane, chlorobenzene; back electrode material: silver (99.99% purity); encapsulation material: UV-curable resin.

[0012] 2. Synthesis Method (1) Synthesis of CdSe / ZnS quantum dots (thermal injection method) ① Precursor preparation: 0.5 mmol cadmium chloride was mixed with 2 mL oleic acid and 3 mL oleylamine, and heated under vacuum at 120 °C for 30 minutes to prepare a cadmium precursor solution; 0.5 mmol selenium powder was dissolved in 5 mL trioctylphosphine and ultrasonically dispersed for 30 minutes to prepare a selenium precursor solution; 1 mmol zinc chloride was mixed with 2 mL oleic acid and 3 mL oleylamine, and heated under vacuum at 120 °C for 30 minutes to prepare a zinc precursor solution; 1 mmol sulfur powder was dissolved in 5 mL trioctylphosphine and ultrasonically dispersed for 30 minutes to prepare a sulfur precursor solution. ②Nucleosynthesis: Mix 1 mL of oleic acid, 1 mL of oleylamine, and 20 mL of octadecene and heat to 290°C. Quickly inject the cadmium precursor solution and selenium precursor solution, and react at a constant temperature for 20 minutes to form CdSe nuclei. ③ Shell coating: The reaction temperature was lowered to 230℃, and zinc precursor solution and sulfur precursor solution were injected at a constant rate of 1 mL / min. The reaction was carried out at 230℃ for 15 minutes to complete the initial deposition of the shell. Then, the temperature was increased to 250℃ in stages at a rate of 5℃ / min, and the reaction was carried out at a constant temperature for 40 minutes to complete the crystallization of the shell. ④ Purification: After cooling to room temperature, add anhydrous ethanol and centrifuge to wash the precipitate. Wash 3 times and dry the precipitate under vacuum at 60°C for 2 hours to obtain CdSe / ZnS core-shell quantum dots (particle size 6 nm, fluorescence yield 80%).

[0013] (2) Substrate pretreatment: The PET substrate was ultrasonically cleaned with deionized water, ethanol and acetone for 15 minutes each, and then vacuum dried at 80°C for 2 hours. (3) Preparation of transparent electrode: PEDOT:PSS aqueous solution was spin-coated onto the pretreated substrate surface at a spin speed of 3000 rpm for 30 seconds, and annealed at 120℃ for 30 minutes to form a uniform transparent conductive layer with a thickness of 50 nm. (4) Synthesis of photoelectric conversion layer: P3HT and PCBM were dissolved in chlorobenzene at a ratio of 1:0.8 to prepare a 20 mg / mL solution. The solution was spin-coated at 2000 rpm for 40 seconds in a nitrogen glove box and annealed at 150°C for 10 minutes to form a 100 nm thick photoelectric conversion layer. (5) Synthesis of quantum dot spectrally selective absorption layer: CdSe / ZnS quantum dots were dispersed in n-hexane, a 5 mg / mL solution was prepared, and the solution was coated by scraping (5 mm / s) and dried under vacuum at 70 °C for 1 hour to form a quantum dot spectrally selective absorption layer; (6) Back electrode fabrication: A 15nm ultrathin silver semi-transparent back electrode was vacuum-deposited on the surface of the quantum dot spectrally selective absorption layer using a full-coverage deposition method with a vacuum degree of 5×10⁻⁶. -4 Pa, speed 1 Å / s; (7) Encapsulation: UV-curable resin coating, UV irradiation for 30 seconds for curing, to obtain as shown Figure 1 The photoelectric conversion thin film with the structure shown.

[0014] 3. Performance Testing Figure 2 This is a spectral response curve of the thin film of the present invention, used to verify the spectral selective absorption and transmission effects.

[0015] Spectral transmittance: Spectrophotometer tests showed 86% transmittance for blue light at 450nm and 88% transmittance for red light at 660nm. Figure 3 ); Photovoltaic conversion efficiency: Tested using a solar simulator (AM1.5G), the conversion efficiency reached 6.3% under ultraviolet, green, and near-infrared light irradiation. Figure 3 ); Weather resistance: After being placed in an environment of 85℃ and 60% relative humidity for 500 hours, the transmittance and conversion efficiency are both maintained at ≥86%.

[0016] Example 2: Preparation of CdTe / ZnS quantum dot + perovskite photoelectric conversion thin film 1. Material preparation Quantum dot synthesis materials: cadmium nitrate, tellurium powder, zinc nitrate, sulfur powder, oleic acid, oleylamine, trioctylphosphine, octadecene (all analytical grade); substrate: PEN thin film (80 μm thick); transparent conductive layer material: ITO sputtered film; photoelectric conversion layer: perovskite material Cs 0.1 FA0.9 PbI 2.8 Br 0.2 Quantum dot: CdTe / ZnS core-shell quantum dot; Back electrode: Silver (99.99% purity); Encapsulation material: Polyimide film.

[0017] 2. Synthesis Steps (1) Synthesis of CdTe / ZnS quantum dots (thermal injection method) ① Precursor preparation: 0.5 mmol cadmium nitrate was mixed with 2 mL oleic acid and 3 mL oleylamine, and heated under vacuum at 120 °C for 30 minutes to obtain a cadmium precursor solution; 0.5 mmol tellurium powder was dissolved in 5 mL trioctylphosphine and ultrasonically dispersed for 30 minutes to obtain a tellurium precursor solution; 1.5 mmol zinc nitrate was mixed with 2 mL oleic acid and 3 mL oleylamine, and heated under vacuum at 120 °C for 30 minutes to obtain a zinc precursor solution; 1.5 mmol sulfur powder was dissolved in 5 mL trioctylphosphine and ultrasonically dispersed for 30 minutes to obtain a sulfur precursor solution. ②Nucleosynthesis: Mix 1 mL of oleic acid, 1 mL of oleylamine and 20 mL of octadecene and heat to 280°C. Quickly inject the cadmium precursor and tellurium precursor solution and react at a constant temperature for 15 minutes to form CdTe nuclei. ③ Shell coating: The reaction temperature was lowered to 220℃, and the zinc precursor and sulfur precursor solution were injected at a constant rate of 1 mL / min. The reaction was carried out at 220℃ for 15 minutes. Then the temperature was increased to 240℃ in stages at 5℃ / min and the reaction was carried out at 240℃ for 50 minutes. ④ Purification: After cooling to room temperature, add anhydrous ethanol and centrifuge to wash the precipitate. Wash 3 times and dry the precipitate under vacuum at 60°C for 2 hours to obtain CdTe / ZnS core-shell quantum dots (particle size 8 nm, fluorescence yield 78%).

[0018] (2) Substrate pretreatment: PEN substrate plasma cleaning for 5 minutes to improve surface adhesion; (3) Transparent electrode: ITO film was prepared by magnetron sputtering, and the sheet resistance was measured by spectrophotometer to be ≤15Ω / sq; (4) Photoelectric conversion layer: Spin-coat 40wt% perovskite precursor solution (6000rpm, 30 seconds), add chlorobenzene antisolvent dropwise at the 10th second of spin coating; heat the hot plate to 100℃ at 5℃ / min, anneal for 15 minutes to form an 80–120nm perovskite photoelectric conversion layer.

[0019] (5) Quantum dot spectrally selective absorption layer: CdTe / ZnS quantum dots were dissolved in 7 mg / mL chlorobenzene, spin-coated at 2500 rpm, and dried at 80 °C for 1 hour; (6) Back electrode: Vacuum evaporation of 15nm ultrathin silver semi-transparent back electrode at a rate of 0.9Å / s, full coverage deposition; (7) Encapsulation: Polyimide film hot-press encapsulation at 80℃ and 0.5MPa.

[0020] 3. Performance Testing Spectral transmittance: 87% blue light transmittance at 450nm, 89% red light transmittance at 660nm; Photoelectric conversion efficiency: 7.5% at AM1.5G; Weather resistance: After 500 hours of aging test, the performance retention rate is ≥88%.

[0021] Example 3: Preparation of PbS / CdS quantum dot + perovskite photoelectric conversion thin film 1. Material Preparation: Quantum dot synthesis materials: lead chloride, sulfur powder, cadmium chloride, oleic acid, oleylamine, trioctylphosphine, octadecene (all analytical grade); Substrate: PC polycarbonate film (100μm thick); Transparent conductive layer material: ITO transparent conductive layer; Photoelectric conversion layer: Cs 0.1 FA 0.9 PbI 2.8 Br 0.2 Perovskite material; Quantum dots: PbS / CdS core-shell quantum dots; Back electrode: Silver (99.99% purity); Encapsulation material: UV-cured resin.

[0022] 2. Synthesis steps (1) Synthesis of PbS / CdS quantum dots (thermal injection method) ① Precursor preparation: 0.5 mmol lead chloride was mixed with 2 mL oleic acid and 3 mL oleylamine, and heated under vacuum at 120 °C for 30 minutes to obtain a lead precursor solution; 0.5 mmol sulfur powder was dissolved in 5 mL trioctylphosphine and ultrasonically dispersed for 30 minutes to obtain a sulfur precursor solution; 1.0 mmol cadmium chloride was mixed with 2 mL oleic acid and 3 mL oleylamine, and heated under vacuum at 120 °C for 30 minutes to obtain a cadmium precursor solution; ②Nucleosynthesis: Mix 1 mL of oleic acid, 1 mL of oleylamine, and 20 mL of octadecene and heat to 280°C. Quickly inject the mixture into the lead precursor solution and the sulfur precursor solution, and react at a constant temperature for 20 minutes to form monodisperse PbS quantum dot nuclei. ③ Shell coating: The reaction system was cooled to 230℃, and the cadmium precursor solution was injected at a constant rate of 1 mL / min. The reaction was carried out at 230℃ for 15 minutes to complete the initial deposition of the CdS shell. Then, the temperature was increased to 250℃ in stages at 5℃ / min, and the reaction was carried out at 250℃ for 40 minutes to complete the shell crystallization. ④ Purification: After cooling to room temperature, add anhydrous ethanol, centrifuge and wash 3 times, and dry under vacuum at 60℃ for 2 hours to obtain PbS / CdS core-shell quantum dots (particle size 9nm, fluorescence yield 76%).

[0023] (2) Substrate pretreatment: PC polycarbonate substrate was ultrasonically cleaned with deionized water, ethanol and acetone for 15 minutes in sequence, and vacuum dried at 80°C for 2 hours; (3) Preparation of transparent electrode: ITO transparent conductive layer with a thickness of 60 nm and sheet resistance ≤15 Ω / □ was prepared by magnetron sputtering; (4) Preparation of photoelectric conversion layer: Spin-coating 40wt% perovskite precursor solution at 6000rpm for 30 seconds, and adding chlorobenzene antisolvent at the 10th second; heating to 100℃ at 5℃ / min and annealing for 15 minutes to form 80–120nm perovskite photoelectric conversion layer. (5) Quantum dot spectrally selective absorption layer: PbS / CdS quantum dots were dispersed in chlorobenzene to prepare a 6 mg / mL solution, spin-coated at 2500 rpm, and dried at 80 °C for 1 hour to form a uniform spectrally selective absorption layer. (6) Back electrode preparation: 15nm ultrathin silver semi-transparent back electrode was vacuum evaporated, with full coverage deposition and a rate of 0.9Å / s; (7) Encapsulation: UV-curable resin coating, UV light irradiation for 30 seconds for curing.

[0024] 3. Performance Testing Spectral transmittance: 85% blue light transmittance at 450nm, 87% red light transmittance at 660nm; Photovoltaic conversion efficiency: 6.8% under simulated sunlight with AM1.5G; Weather resistance: After being placed in an environment of 85℃ and 60% humidity for 500 hours, the performance retention rate is ≥87%.

Claims

1. A method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation, characterized in that, The steps are as follows: (1) Select a transparent flexible polymer film as the substrate, and clean and dry it to remove surface impurities; (2) A transparent conductive layer with a thickness of 40-60 nm is prepared on the pretreated substrate surface by spin coating or sputtering. (3) A photoelectric conversion material is coated on the surface of the transparent conductive layer, and after annealing and curing, a photoelectric conversion layer is formed on the transparent conductive layer; (4) Core-shell structured quantum dots are synthesized by hot injection method, and then dispersed in organic solvent to prepare a quantum dot solution with a concentration of 3-8 mg / mL. The solution is then coated onto the surface of the photoelectric conversion layer by spin coating or blade coating, and dried to form a quantum dot spectrally selective absorption layer. (5) A metal back electrode layer is prepared on the surface of the quantum dot spectrally selective absorption layer by vacuum evaporation; (6) The multilayer composite structure material prepared above is encapsulated as a whole to obtain an agricultural photoelectric conversion film; The quantum dot spectrally selective absorption layer absorbs light in the first preset wavelength band and guides it to the photoelectric conversion layer, with a transmittance of ≥80% for light in the second preset wavelength band. The first preset wavelength band includes ultraviolet light with a wavelength <400nm, green light with a wavelength of 500-600nm, and / or near-infrared light with a wavelength >700nm. The second preset wavelength band includes blue light with a wavelength of 400-500nm and red light with a wavelength of 600-700nm.

2. The method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation according to claim 1, characterized in that: The polymer film is a transparent flexible film of polyethylene terephthalate, polyethylene naphthalate, or polycarbonate, with a thickness of 80-120 μm.

3. The method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation according to claim 1, characterized in that: The transparent conductive layer material is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate or indium tin oxide, with a thickness of 40-60 nm.

4. The method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation according to claim 1, characterized in that: The photoelectric conversion materials are poly(3-hexylthiophene) and (6,6)-phenyl-C 61 A mixture of methyl butyrate and perovskite materials, with a coating thickness of 80-120 nm.

5. The method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation according to claim 1, characterized in that: In step (4), the core-shell structured quantum dots are CdSe / ZnS, CdTe / ZnS or PbS / CdS, with a particle size of 5-10 nm and a fluorescence yield of ≥75%; the concentration of the quantum dot solution is 3-8 mg / mL, and it is prepared using n-hexane, chlorobenzene or toluene; The synthesis of the core-shell quantum dots is as follows: ①Preparation of metal precursor solutions, non-metal precursor solutions, and shell precursor solutions; ② Heat the octadecene solvent containing oleic acid, oleylamine or trioctylphosphine ligand to 280-300℃, and rapidly inject it into the metal precursor solution and non-metal precursor solution. React at 280-300℃ for 10-30 minutes to form monodisperse quantum dot cores. ③ Reduce the temperature of the reaction system to the basic coating temperature of 220-250℃, inject the shell precursor solution at a rate of 0.5-2 mL / min, and react at a constant temperature of 220-250℃ for 10-20 minutes. Then, increase the temperature in stages to the crystallization temperature of 240-260℃ at a heating rate of 5-10℃ / min and react at a constant temperature for 10-40 minutes. Centrifuge, wash the solid, and dry to obtain core-shell structured quantum dots. The core-shell quantum dot is configured to selectively absorb ultraviolet light with wavelengths <400nm, green light with wavelengths of 500-600nm, and near-infrared light with wavelengths >700nm, and guide the absorbed light energy to the photoelectric conversion layer through exciton energy transfer to achieve photoelectric conversion; the transmittance of ≥85% for blue light with wavelengths of 400-500nm and red light with wavelengths of 600-700nm, which are essential for plant photosynthesis.

6. The method for synthesizing agricultural photoelectric conversion thin films based on selective spectral modulation according to claim 5, characterized in that: The metal back electrode is an ultra-thin, semi-transparent silver back electrode with a thickness of 10-20 nm, and the electrode adopts full-coverage deposition.

7. The agricultural photoelectric conversion film prepared by the selective spectral modulation method for synthesizing agricultural photoelectric conversion films according to any one of claims 1-6.

8. The application of the agricultural photoelectric conversion film according to claim 7 as a covering for agricultural facilities.

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